As is known in the art, in one type of data storage system, storage processors are used to provide a system interface between a host computer/server and a bank of disk drives. In one of such system, a midplane is provided having the storage processors and power supplies plugged into one side, say the front side of a printed circuit board, commonly referred to as a midplane, and disk drive units plugged into the other side, say back side, of the midplane. Typically, a pair of storage processors and a pair of power supplies is provided for redundancy
One such arrangement for such a system is to provide a rack-mounted configuration wherein the power supplies and storage processors are disposed in rack mountable chassis; for example, the power supply chassis are mounted in a side-by-side arrangement on say a top rack while the storage processor chassis are mounted side-by-side below the power supply chassis on a lower rack. In one such system fans are provided in each of the power supplies along with fan controllers for adjusting fan speed in accordance with a desired temperature signal fed by microprocessors in the storage processor chassis in response to temperature sensors disposed in the path of air flow used to cool the disk drives. More particularly, in order to cool the disk drives in accordance with the temperature signal, the fans draw air that passes along the outer sides of the disk drive units, then through air flow channels in the midplane, then through openings in the rear of the storage processor chassis, then through openings in the upper portion of the storage processor chassis, then into openings in the bottom portion of the power supply chassis (which, as noted above, store the fans) and then finally out the front of the power supply chassis.
As noted above, temperature sensors provide the information on which cooling fan speeds are changed. In low temperature environments, fans can be operated at lower speeds with the ensuing benefit of lower noise and lower power consumption. These sensors also provide information on excessive ambient temperature conditions which could damage systems or result in loss of critical data if the system were not shut down. Multiple sensors are sometimes utilized to allow for sensor failures without requiring the system to be shutdown for lack of information on which to base the speed changes and shutdown decisions outlined above. The sensor issue is further complicated by the fact that the sensors are located in air streams which are preheated by upstream electronics. This is a result of a combination of system architecture (such as drives mounted in the front of a front-to-rear cooled enclosure) and the sensors being located on the first available printed circuit board (PCB) in the system.
Thus, two major issues present themselves:                First, using multiple sensors, so that backup information is available in the result of a sensor failure, requires that a failed sensor be identified and its reading ignored. A failed sensor may not only present no data but may also present false data. Therefore, some algorithm must be adopted to cull out or ignore the false sensor readings.        Second, a change in fan speed results in a change in air preheat as the air stream flows over upstream electronics. As a result, the sensor to ambient temperature difference decreases as the fan speed increases. Consequently, the sensor temperature where the fan speed is increased has to be higher than the temperature where the fan speed is lowered. A resulting hysteresis is often observed in these systems.        
In accordance with the present invention, a method is provided for cooling a data storage system. The system includes a midplane with an electrical chassis connected to one side of the midplane and a disk drive connected to an opposite side of the midplane. The chassis has therein a fan for forcing air past the disk drive and channels in the midplane. The midplane has a plurality of temperature sensors mounted thereto, such plurality of temperature sensors being disposed to detect the temperature of the air flow passing through the channels. The fan has the speed thereof controlled in response to a temperature control signal. The method includes: detecting temperature signals produced by the plurality of temperature sensors; comparing differences between the detected temperature signals; and selecting one of the detected temperature control signals from the compared differences as the temperature control signal.
In one embodiment, the selecting includes disregarding at least one of the detected temperature signals as the temperature control signal.
In one embodiment, the selecting includes selecting the hottest one of the detected signals as the temperature control signal unless the compared differences indicates that one of the differences in temperature is greater than a predetermined temperature difference in which case a lower temperature than the hottest temperature is selected as the temperature control signal.
In one embodiment, a method is provided for detected a faulty one of a plurality of temperature sensors. The method includes: detecting temperature signals produced by the plurality of temperature sensors; comparing differences between the detected temperature signals; selecting one of the detected temperature control signals as the faulty one of the plurality of temperature sensors from the compared differences.
In one embodiment, a system is provided having: a midplane having air flow channels therein; a disk drive mounted to a first side of the midplane; and a plurality of temperature sensors mounted to the midplane. The system includes; a pair of electrical chassis connected to a second side of the midplane. A first one of the pair of chassis has therein: a fan; and a fan controller for controlling speed of the fan in response to a temperature control signal. A second one of the pair of chassis has therein: a microprocessor for: detecting temperature signals produced by the plurality of temperature sensors; comparing differences between the detected temperature signals; and selecting one of the detected temperature control signal from the compared differences as the temperature control signal.
In one embodiment, the fans draw air past the disk drives and through the channels in the midplane.
In one embodiment, the plurality of temperature sensors is disposed to detect the temperature of air flowing through the channels.
In one embodiment, a system is provided having a midplane having air flow channels therein. The system includes a first pair of electrical chassis connected to a first side of the midplane and a second pair of electrical chassis connected to the first side of the midplane. A plurality of disk drives is connected to a second side of the midplane. A pair of fans is provided, each one of the fans being disposed in a corresponding one of the first pair of electrical chassis. A pair of fan controllers is provided, each one of the fan controllers being disposed in a corresponding one of the first pair of electrical chassis, each one of the fan controllers controlling speed of a corresponding one of the fans in response to a common temperature control signal. The fans draw air past the disk drives and through channels in the midplane. A plurality of temperature sensors is mounted to the midplane, such a plurality of temperature sensors being disposed to detect the temperature of the air flow passing through the channels. A pair of microprocessors is provided, each one being disposed in a corresponding one of the pair of second chassis, one of the pair of such microprocessors being selected to: detect temperature signals produced by the plurality of temperature sensors; compare differences between the detected temperature signals; and select one of the detected temperature control signal from the compared differences as the common temperature control signal.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.